In the field of integrated optics, there may be a need to use a mode conversion device, such as a mode converter (MC).
European Patent Application EP-0513919-A1 to Van Der Tol describes a passive device for mode conversion of a first mode into a second pre-defined mode. The device is described to include a periodic geometrical structure consisting of a periodic sequence of two wave-guiding subsections within each period, wherein the lengths of the subsections and the number of periods being matched to a pre-determined conversion fraction may be designed to allow coupling of a first pre-defined guided mode to a second pre-defined guided mode. Similar devices are also described in U.S. Pat. No. 5,703,977 to Pedersen et al and in European Patent Application EP0645650A1 to Van Der Tol. In such passive devices, the fraction of light being converted is pre-determined by the geometry of the device and, therefore, the activation and operation of such devices cannot be selectively adjusted or controlled.
U.S. Pat. No. 5,574,808 to Van Der Tol et al describes a mechanism for activating and de-activating a mode-conversion device. The described device is activated by activating an electrode designed to disrupt the coupling between guided modes of the device, thereby to convert the coupling of a signal from a first guided mode to a second guided mode.